An electronic component storing package such as an SMD (Surface Mount Device) package (surface mount device package) employed for hermetically sealing an electronic component such as a SAW filter (surface acoustic wave filter) or a quartz resonator employed for removing noise from a portable telephone or the like is known in general. This electronic component storing package is disclosed in Japanese Patent Laid-Open No. 2000-150687, for example. A hermetic sealing cap is employed when hermetically sealing such an electronic component storing package.
FIG. 17 is a sectional view showing the overall structure of an electronic component storing package for storing an electronic component according to exemplary prior art. Referring to FIG. 17, an insulating ceramic frame body 102 is formed on an end face of an insulating ceramic substrate 101 to constitute a storage space in the electronic component according to the exemplary prior art. An electronic component 105 such as a quartz resonator is mounted onto the ceramic substrate 101 located in the storage space enclosed with the ceramic frame body 102 through bumps 104. A hermetic sealing cap member 111 is bonded onto the ceramic frame body 102 through a solder layer 103 serving as a sealant.
A nickel plating layer 112 is formed to cover the whole of the surfaces of the hermetic sealing cap member 111. A gold plating layer 113 is formed to cover the whole of the surfaces of the nickel plating layer 112. The gold plating layer 113 is provided in order to improve bondability to the solder layer 103 consisting of gold-tin solder, and the nickel plating layer 112 is provided as an undercoat layer for the gold plating layer 113.
A manufacturing process for a hermetic sealing package employed for the electronic component storing package shown in FIG. 17 is described with reference to FIGS. 18 and 19.
As shown in FIG. 18, the platelike hermetic sealing cap member 111 consisting of an iron-nickel-cobalt (Fe—Ni—Co) alloy is formed by press working. The nickel plating layer 112 is formed on the overall surfaces of the hermetic sealing cap member 111 as the undercoat layer, and the gold plating layer 113 is thereafter formed to cover the overall surfaces of the nickel plating layer 112.
As shown in FIG. 19, the solder layer 103 consisting of the gold-tin (Au—Sn) solder is temporarily brazed to portions of the surfaces of the gold plating layer 113 of the hermetic sealing cap member 111 bonded to the ceramic frame body 102. As shown in FIG. 17, the solder layer 103 temporarily brazed to the hermetic sealing cap member 111 is arranged to be in contact with the upper surface of the ceramic frame body 102 of the ceramic substrate 101 mounted with the electronic component 105 through the bumps 104. Thereafter the solder layer 103 is so melted as to bond the hermetic sealing cap member 111 to the upper surface of the ceramic frame body 102. Thus, the conventional electronic component storing package shown in FIG. 17 is formed.
In the conventional electronic component storing package shown in FIG. 17, however, there has been such an inconvenience that the number of components is increased since the substrate side is in the two-layer structure of the ceramic substrate 101 and the ceramic frame body 102.
In general, therefore, there is proposed an electronic component storing package according to another exemplary prior art forming a substrate side by a single layer while bringing a hermetic sealing cap into a structure having a cavity portion (recess portion) thereby reducing the number of components. FIG. 20 is a sectional view showing the electronic component storing package according to the other exemplary prior art. Referring to FIG. 20, the substrate side is constituted of a single-layer insulating ceramic substrate 131 in this electronic component storing package according to the other exemplary prior art. An electronic component 134 such as a quartz resonator is mounted onto a prescribed region of the ceramic substrate 131 through bumps 133. A hermetic sealing cap member 141 having a cavity portion (recess portion) is mounted through a solder layer 132 consisting of gold-tin (Au—Sn) solder, to seal the ceramic substrate 131. A nickel plating layer 142 serving as an undercoat layer is formed to cover the overall surfaces of the hermetic sealing cap member 141. A gold plating layer 143 is formed to cover the overall surfaces of the nickel plating layer 142.
As a manufacturing process for the electronic component storing package according to the other exemplary prior art shown in FIG. 20, a rough structure of the hermetic sealing cap member 141 having a flange portion 141a and the cavity portion (recess portion) 160 is formed in a first drawing step shown in FIG. 21. A second drawing step shown in FIG. 22 and a third drawing step shown in FIG. 23 are so carried out that the hermetic sealing cap member 141 including the flange portion 141a having a flat portion 141c shown in FIG. 23 is formed.
As shown in FIG. 24, the nickel plating layer 142 serving as the undercoat layer is formed to cover the overall surfaces of the hermetic sealing cap member 141. The gold plating layer 143 is formed to cover the overall surfaces of the nickel plating layer 142.
As shown in FIG. 25, the solder layer 132 consisting of the gold-tin solder is temporarily brazed onto the gold plating layer 143 corresponding to the flange portion 141a of the hermetic sealing cap member 141. As shown in FIG. 20, the solder layer 132 temporarily brazed to the hermetic sealing cap member 141 is arranged to be in contact with the upper surface of the ceramic substrate 131 mounted with the electronic component 134 through the bumps 133. Thereafter the solder layer 132 is so melted as to bond the hermetic sealing cap member 141 to the upper surface of the ceramic substrate 131. Thus, the electronic component storing package according to the other exemplary prior art shown in FIG. 20 is formed.
In the hermetic sealing cap employed for the electronic component storing package according to the exemplary prior art shown in FIG. 17 and the hermetic sealing cap employed for the electronic component storing package according to the other exemplary prior art shown in FIG. 20, however, there have been problems shown in FIGS. 26 and 27 respectively.
In the hermetic sealing cap member 111 according to the exemplary prior art shown in FIG. 17, the gold plating layer 113 is formed on the overall surfaces of the hermetic sealing cap member 111 through the nickel plating layer 112 serving as the undercoat layer. This gold plating layer 113 is so excellent in wettability with the solder layer 103 consisting of the gold-tin solder that the solder layer 103 disadvantageously flows into the side where the electronic component 105 is stored as shown in FIG. 26. When the solder layer 103 has thus flowed into the inner side, the influent solder layer 103 may have so scattered toward the electronic component 105 that the electronic component 105 and the solder layer 103 have come into contact with each other. There has been such a problem that device characteristics of the electronic component 105 are deteriorated in this case.
Also in the hermetic sealing cap member 141 having the cavity portion according to the other exemplary prior art shown in FIG. 20, the gold plating layer 143 is formed on the overall surfaces through the nickel plating layer 142 serving as the undercoat layer, and hence the solder layer 132 creeps up to the inner surface of the hermetic sealing cap member 141 when sealing the hermetic sealing cap member 141 to the ceramic substrate 131 with the solder layer 132, as shown in FIG. 27. When the solder layer 132 has thus crept up to the inner surface of the hermetic sealing cap member 141, the creeping solder layer 132 may have so scattered toward the electronic component 134 that the solder layer 132 and the electronic component 134 have come into contact with each other. There has been such a problem that device characteristics of the electronic component 134 are reduced in this case.
In the hermetic sealing cap member 141 having the cavity portion according to the other exemplary prior art shown in FIG. 20, further, the flange portion 141a is formed through the conventional general drawing steps shown in FIGS. 21 to 23 and hence a sealing side inner corner portion 141b of the flange portion 141a is brought into a rounded shape. In other words, there has been such a disadvantage that the radius of curvature of the sealing side inner corner portion 141b of the flange portion 141a is so increased that the length of the flat portion 141c of the flange portion 141a is reduced. If the length of the flat portion 141c of the flange portion 141a is reduced, there is such a problem that the length of a sealing surface is so reduced that sealing properties are deteriorated. In this case, further, there has been such a problem that the outside dimensions of the hermetic sealing cap member 141 are so increased that it is difficult to attain miniaturization as a result if an attempt is made to increase the length of the flat portion 141c of the flange portion 141a in order improve the sealing properties.